CH3I Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

CH3I lewis structure has a Carbon atom (C) at the center which is surrounded by three Hydrogen atoms (H) and one Iodine atom (I). There is a single bond between the Carbon (C) & Iodine (I) atom as well as between the Carbon (C) and Hydrogen (H) atoms. There are 3 lone pairs on the Iodine atom (I). 

If you haven’t understood anything from the above image of CH3I lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of CH3I.

So let’s move to the steps of drawing the lewis structure of CH3I.

Steps of drawing CH3I lewis structure

Step 1: Find the total valence electrons in CH3I molecule

In order to find the total valence electrons in a CH3I molecule, first of all you should know the valence electrons present in carbon atom, hydrogen atom as well as iodine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of carbon, hydrogen as well as iodine using a periodic table.

Total valence electrons in CH3I molecule

→ Valence electrons given by carbon atom:

Carbon is group 14 element on the periodic table. ^[1] Hence the valence electrons present in carbon is 4.

You can see the 4 valence electrons present in the carbon atom as shown in the above image.

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[2] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

→ Valence electrons given by iodine atom:

Iodine is a group 17 element on the periodic table. ^[3] Hence the valence electrons present in iodine is 7.

You can see the 7 valence electrons present in the iodine atom as shown in the above image.

Hence, 

Total valence electrons in CH3I molecule = valence electrons given by 1 carbon atom + valence electrons given by 3 hydrogen atoms + valence electrons given by 1 iodine atom = 4 + 1(3) + 7 = 14.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given molecule is CH3I and it contains carbon atom (C), hydrogen atoms (H) and iodine atom (I).

So as per the rule we have to keep hydrogen outside.

Now, you can see the electronegativity values of carbon atom (C) and iodine atom (I) in the above periodic table.

If we compare the electronegativity values of carbon (C) and iodine (I) then the carbon atom is less electronegative.

So here the carbon atom (C) is the center atom and the iodine atom (I) is the outside atom.

Step 3: Connect each atoms by putting an electron pair between them

Now in the CH3I molecule, you have to put the electron pairs between the carbon (C) & iodine (I) atom and between the carbon (C) & hydrogen (H) atoms.

This indicates that these atoms are chemically bonded with each other in a CH3I molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of CH3I molecule, you can see that the outer atoms are hydrogen atoms and iodine atom.

These hydrogen atoms and iodine atom are forming a duplet and octet respectively and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the CH3I molecule.

The CH3I molecule has a total 14 valence electrons and all these valence electrons are used in the above sketch of CH3I.

Hence there are no remaining electron pairs to be kept on the central atom. 

So now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central carbon atom (C) is stable or not.

In order to check the stability of the central carbon (C) atom, we have to check whether it is forming an octet or not.

You can see from the above picture that the carbon atom is forming an octet. That means it has 8 electrons.

And hence the central carbon atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of CH3I is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of CH3I.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on carbon (C) atom, hydrogen (H) atoms as well as iodine (I) atom present in the CH3I molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of CH3I molecule in the image given below.

For Carbon (C) atom:
Valence electrons = 4 (because carbon is in group 14)
Bonding electrons = 8
Nonbonding electrons = 0

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

For Iodine (I) atom:
Valence electron = 7 (because iodine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
C	=	4	–	8/2	–	0	=	0
H	=	1	–	2/2	–	0	=	0
I	=	7	–	2/2	–	6	=	0

From the above calculations of formal charge, you can see that the carbon (C) atom, hydrogen (H) atom as well as iodine (I) atom have a “zero” formal charge.

This indicates that the above lewis structure of CH3I is stable and there is no further change in the above structure of CH3I.

In the above lewis dot structure of CH3I, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of CH3I.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

BrO- Lewis Structure	SeOF2 Lewis Structure
SBr6 Lewis Structure	IO3- Lewis Structure
HOFO Lewis Structure	BrF Lewis Structure